1. Field of the Invention
The present invention is directed to a keyless chuck adapted to releasably hold a tool bit such as a drill bit of a power drill or the like rotary power tools, and more particularly to a chuck for rotary power tools capable of reversely rotating the tool bit.
2. Description of the Prior Art
Keyless chucks are known in the art in which a set of gripping jaws are tightened on a tool bit by manipulating a handle ring to rotate independently of a driving connection from a drive source to the tool bit. Such handle ring is generally located around a chuck body which carries the gripping jaws and is adapted to be coupled to a drive spindle of the drive source for establishing the driving connection. The handle ring is rotatable around the chuck body and is operatively connected to the gripping jaws in such a way as to tighten and loosen the same on the tool bit upon being selectively rotated relative to the chuck body. The handle ring is coupled to the chuck body by a one-way clutch which acts to rotatively fix the handle ring to the chuck for preventing the handle ring from counter-rotating in the direction of loosening the gripping jaws when the chuck body is driven to rotate in the reverse direction, thus enabling to turning the tool bit reversely without disengaging the tool bit from the gripping jaws. Further, the one-way clutch allows the handle ring to rotate relative to the chuck body in the direction of tightening the gripping jaws until the gripping jaws are tightened on the tool bit to be rotatable therewith, whereby enabling a self-tightening of the gripping jaws on the tool bit. When removing or disengaging the tool bit from the gripping jaws, the one-way clutch is required to be shifted to a release position of disengaging the handle ring from the chuck body, permitting the handle ring to rotate freely from the chuck body to loosen the gripping jaws. To this end, prior chucks have been devised to provide a separate release ring for disengaging the clutch to loosen the gripping jaws, in addition to the handle ring utilized to tighten the gripping jaws, as seen in U.S. Pat. No. 4,302,021. However, such separate provision of the handle ring and the release ring is found inconvenient and requires a complicated assembly with an attendant increase in the number of parts employed. To overcome this problems, U.S. Pat. No. 4,695,065 assigned to the same assignee of the subject application discloses to use a single handle ring for tightening and loosing the gripping jaws. However, in this patent, the handle ring is required to be shifted axially for releasing the clutch and then be manipulated to rotate in a given direction to loosen the gripping jaws out of the tool bit. In this sense, the chuck of the patent also requires a rather complicated manipulation and is therefore found not to be satisfactory in providing a simple or instinctive loosening operation of releasing the clutch and disengaging the tool bit from the gripping jaws.